Systems and methods for detecting a tilt angle from a depth image

ABSTRACT

A depth image of a scene may be received, observed, or captured by a device. A human target in the depth image may then be scanned for one or more body parts such as shoulders, hips, knees, or the like. A tilt angle may then be calculated based on the body parts. For example, a first portion of pixels associated with an upper body part such as the shoulders and a second portion of pixels associated with a lower body part such as a midpoint between the hips and knees may be selected. The tilt angle may then be calculated using the first and second portions of pixels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/959,480 filed Aug. 5, 2013, which is a continuation of U.S. patentapplication Ser. No. 13/713,526 filed Dec. 13, 2012, now U.S. Pat. No.8,503,766 issued Aug. 6, 2013, which is a continuation of U.S. patentapplication Ser. No. 12/485,804, filed Jun. 16, 2009, now U.S. Pat. No.8,340,432 issued Dec. 25, 2012, which claims the benefit under 35 U.S.C.§119(e) of U.S. Provisional Patent Application No. 61/174,973 filed May1, 2009, the disclosures of which are incorporated herein by reference.

BACKGROUND

Many computing applications such as computer games, multimediaapplications, or the like use controls to allow users to manipulate gamecharacters or other aspects of an application. Typically such controlsare input using, for example, controllers, remotes, keyboards, mice, orthe like. Unfortunately, such controls can be difficult to learn, thuscreating a barrier between a user and such games and applications.Furthermore, such controls may be different than actual game actions orother application actions for which the controls are used. For example,a game control that causes a game character to swing a baseball bat maynot correspond to an actual motion of swinging the baseball bat.

SUMMARY

Disclosed herein are systems and methods for detecting a tilt angle froma depth image. For example, a depth image of a scene may be received,captured, or observed by, for example, a capture device. The depth imagemay then be analyzed to determine whether the image includes a humantarget associated with a user. If the image includes a human targetassociated with a user, the human target may be scanned to determine,for example, a location and/or measurements of one or more body parts.According to an example embodiment, a tilt angle may be calculated basedon the body scan. For example, the capture device may be tilted upwardor downward such that information including the depth images captured bythe capture device may be distorted or skewed based on the tilt. Afterscanning the human target, a first portion of the human targetassociated with an upper body part such as the shoulders and a secondportion of the human target associated with a lower body part such as amidpoint between the hips and knees may be used to calculate a tiltangle. For example, in one embodiment, the first and second portions maydefine a line therebetween that may be used to calculate a tangentvalue. According to an example embodiment, the tangent value may be usedto calculate the tilt angle. The tilt angle may then be processed suchthat the tilt angle may be used to adjust, for example, a model byrotating to an upright orientation, a capture device by physicallyrotating the capture device, and/or by transforming an image such as thedepth image, an RGB image, or the like captured by the capture device.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate an example embodiment of a targetrecognition, analysis, and tracking system with a user playing a game.

FIG. 2 illustrates an example embodiment of a capture device that may beused in a target recognition, analysis, and tracking system.

FIG. 3 illustrates an example embodiment of a computing environment thatmay be used to interpret one or more gestures in a target recognition,analysis, and tracking system and/or animate an avatar or on-screencharacter displayed by a target recognition, analysis, and trackingsystem.

FIG. 4 illustrates another example embodiment of a computing environmentthat may be used to interpret one or more gestures in a targetrecognition, analysis, and tracking system and/or animate an avatar oron-screen character displayed by a target recognition, analysis, andtracking system.

FIG. 5 depicts a flow diagram of an example method for detecting a tiltangle of a capture device.

FIG. 6 illustrates an example embodiment of a depth image that may becaptured or observed.

FIG. 7 illustrates an example embodiment of a depth image with a humantarget being scanned.

FIG. 8 illustrates an example embodiment of a depth image with a scannedhuman target.

FIG. 9 illustrates an example embodiment of pixels that may define ahuman target in a depth image.

FIGS. 10A-10B illustrate an example embodiment of portions of pixelsthat may define a human target in a depth image that may be used tocalculate a tilt angle for a capture device.

FIG. 11 illustrates a side view of an example embodiment of a depthimage with a human target that may be tilted.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 1A and 1B illustrate an example embodiment of a configuration of atarget recognition, analysis, and tracking system 10 with a user 18playing a boxing game. In an example embodiment, the target recognition,analysis, and tracking system 10 may be used to recognize, analyze,and/or track a human target such as the user 18.

As shown in FIG. 1A, the target recognition, analysis, and trackingsystem 10 may include a computing environment 12. The computingenvironment 12 may be a computer, a gaming system or console, or thelike. According to an example embodiment, the computing environment 12may include hardware components and/or software components such that thecomputing environment 12 may be used to execute applications such asgaming applications, non-gaming applications, or the like. In oneembodiment, the computing environment 12 may include a processor such asa standardized processor, a specialized processor, a microprocessor, orthe like that may execute instructions including, for example,instructions for receiving a depth image, scanning a human target in thedepth image, and calculating a tilt angle based on the scanned humantarget, or any other suitable instruction, which will be described inmore detail below.

As shown in FIG. 1A, the target recognition, analysis, and trackingsystem 10 may further include a capture device 20. The capture device 20may be, for example, a camera that may be used to visually monitor oneor more users, such as the user 18, such that gestures and/or movementsperformed by the one or more users may be captured, analyzed, andtracked to perform one or more controls or actions within an applicationand/or animate an avatar or on-screen character.

According to one embodiment, the target recognition, analysis, andtracking system 10 may be connected to an audiovisual device 16 such asa television, a monitor, a high-definition television (HDTV), or thelike that may provide game or application visuals and/or audio to a usersuch as the user 18. For example, the computing environment 12 mayinclude a video adapter such as a graphics card and/or an audio adaptersuch as a sound card that may provide audiovisual signals associatedwith the game application, non-game application, or the like. Theaudiovisual device 16 may receive the audiovisual signals from thecomputing environment 12 and may then output the game or applicationvisuals and/or audio associated with the audiovisual signals to the user18. According to one embodiment, the audiovisual device 16 may beconnected to the computing environment 12 via, for example, an S-Videocable, a coaxial cable, an HDMI cable, a DVI cable, a VGA cable, or thelike.

As shown in FIGS. 1A and 1B, the target recognition, analysis, andtracking system 10 may be used to recognize, analyze, and/or track ahuman target such as the user 18. For example, the user 18 may betracked using the capture device 20 such that the gestures and/ormovements of user 18 may be captured to animate an avatar or on-screencharacter and/or may be interpreted as controls that may be used toaffect the application being executed by computer environment 12. Thus,according to one embodiment, the user 18 may move his or her body tocontrol the application and/or animate the avatar or on-screencharacter.

As shown in FIGS. 1A and 1B, in an example embodiment, the applicationexecuting on the computing environment 12 may be a boxing game that theuser 18 may be playing. For example, the computing environment 12 mayuse the audiovisual device 16 to provide a visual representation of aboxing opponent 38 to the user 18. The computing environment 12 may alsouse the audiovisual device 16 to provide a visual representation of aplayer avatar 40 that the user 18 may control with his or her movements.For example, as shown in FIG. 1B, the user 18 may throw a punch inphysical space to cause the player avatar 40 to throw a punch in gamespace. Thus, according to an example embodiment, the computerenvironment 12 and the capture device 20 of the target recognition,analysis, and tracking system 10 may be used to recognize and analyzethe punch of the user 18 in physical space such that the punch may beinterpreted as a game control of the player avatar 40 in game spaceand/or the motion of the punch may be used to animate the player avatar40 in game space.

Other movements by the user 18 may also be interpreted as other controlsor actions and/or used to animate the player avatar, such as controls tobob, weave, shuffle, block, jab, or throw a variety of different powerpunches. Furthermore, some movements may be interpreted as controls thatmay correspond to actions other than controlling the player avatar 40.For example, the player may use movements to end, pause, or save a game,select a level, view high scores, communicate with a friend, etc.Additionally, a full range of motion of the user 18 may be available,used, and analyzed in any suitable manner to interact with anapplication.

In example embodiments, the human target such as the user 18 may have anobject. In such embodiments, the user of an electronic game may beholding the object such that the motions of the player and the objectmay be used to adjust and/or control parameters of the game. Forexample, the motion of a player holding a racket may be tracked andutilized for controlling an on-screen racket in an electronic sportsgame. In another example embodiment, the motion of a player holding anobject may be tracked and utilized for controlling an on-screen weaponin an electronic combat game.

According to other example embodiments, the target recognition,analysis, and tracking system 10 may further be used to interpret targetmovements as operating system and/or application controls that areoutside the realm of games. For example, virtually any controllableaspect of an operating system and/or application may be controlled bymovements of the target such as the user 18.

FIG. 2 illustrates an example embodiment of the capture device 20 thatmay be used in the target recognition, analysis, and tracking system 10.According to an example embodiment, the capture device 20 may beconfigured to capture video with depth information including a depthimage that may include depth values via any suitable techniqueincluding, for example, time-of-flight, structured light, stereo image,or the like. According to one embodiment, the capture device 20 mayorganize the depth information into “Z layers,” or layers that may beperpendicular to a Z axis extending from the depth camera along its lineof sight.

As shown in FIG. 2, the capture device 20 may include an image cameracomponent 22. According to an example embodiment, the image cameracomponent 22 may be a depth camera that may capture the depth image of ascene. The depth image may include a two-dimensional (2-D) pixel area ofthe captured scene where each pixel in the 2-D pixel area may representa depth value such as a length or distance in, for example, centimeters,millimeters, or the like of an object in the captured scene from thecamera.

As shown in FIG. 2, according to an example embodiment, the image cameracomponent 22 may include an IR light component 24, a three-dimensional(3-D) camera 26, and an RGB camera 28 that may be used to capture thedepth image of a scene. For example, in time-of-flight analysis, the IRlight component 24 of the capture device 20 may emit an infrared lightonto the scene and may then use sensors (not shown) to detect thebackscattered light from the surface of one or more targets and objectsin the scene using, for example, the 3-D camera 26 and/or the RGB camera28. In some embodiments, pulsed infrared light may be used such that thetime between an outgoing light pulse and a corresponding incoming lightpulse may be measured and used to determine a physical distance from thecapture device 20 to a particular location on the targets or objects inthe scene. Additionally, in other example embodiments, the phase of theoutgoing light wave may be compared to the phase of the incoming lightwave to determine a phase shift. The phase shift may then be used todetermine a physical distance from the capture device to a particularlocation on the targets or objects.

According to another example embodiment, time-of-flight analysis may beused to indirectly determine a physical distance from the capture device20 to a particular location on the targets or objects by analyzing theintensity of the reflected beam of light over time via varioustechniques including, for example, shuttered light pulse imaging.

In another example embodiment, the capture device 20 may use astructured light to capture depth information. In such an analysis,patterned light (i.e., light displayed as a known pattern such as gridpattern or a stripe pattern) may be projected onto the scene via, forexample, the IR light component 24. Upon striking the surface of one ormore targets or objects in the scene, the pattern may become deformed inresponse. Such a deformation of the pattern may be captured by, forexample, the 3-D camera 26 and/or the RGB camera 28 and may then beanalyzed to determine a physical distance from the capture device to aparticular location on the targets or objects.

According to another embodiment, the capture device 20 may include twoor more physically separated cameras that may view a scene fromdifferent angles to obtain visual stereo data that may be resolved togenerate depth information.

The capture device 20 may further include a microphone 30. Themicrophone 30 may include a transducer or sensor that may receive andconvert sound into an electrical signal. According to one embodiment,the microphone 30 may be used to reduce feedback between the capturedevice 20 and the computing environment 12 in the target recognition,analysis, and tracking system 10. Additionally, the microphone 30 may beused to receive audio signals that may also be provided by the user tocontrol applications such as game applications, non-game applications,or the like that may be executed by the computing environment 12.

In an example embodiment, the capture device 20 may further include aprocessor 32 that may be in operative communication with the imagecamera component 22. The processor 32 may include a standardizedprocessor, a specialized processor, a microprocessor, or the like thatmay execute instructions including, for example, instructions forreceiving a depth image, scanning a human target in the depth image, andcalculating a tilt angle based on the scanned human target, or any othersuitable instruction, which will be described in more detail below.

The capture device 20 may further include a memory component 34 that maystore the instructions that may be executed by the processor 32, imagesor frames of images captured by the 3-D camera or RGB camera, or anyother suitable information, images, or the like. According to an exampleembodiment, the memory component 34 may include random access memory(RAM), read only memory (ROM), cache, Flash memory, a hard disk, or anyother suitable storage component. As shown in FIG. 2, in one embodiment,the memory component 34 may be a separate component in communicationwith the image capture component 22 and the processor 32. According toanother embodiment, the memory component 34 may be integrated into theprocessor 32 and/or the image capture component 22.

As shown in FIG. 2, the capture device 20 may be in communication withthe computing environment 12 via a communication link 36. Thecommunication link 36 may be a wired connection including, for example,a USB connection, a Firewire connection, an Ethernet cable connection,or the like and/or a wireless connection such as a wireless 802.11b, g,a, or n connection. According to one embodiment, the computingenvironment 12 may provide a clock to the capture device 20 that may beused to determine when to capture, for example, a scene via thecommunication link 36.

Additionally, the capture device 20 may provide the depth informationand images captured by, for example, the 3-D camera 26 and/or the RGBcamera 28, and/or a skeletal model that may be generated by the capturedevice 20 to the computing environment 12 via the communication link 36.The computing environment 12 may then use the model, depth information,and captured images to, for example, control an application such as agame or word processor and/or animate an avatar or on-screen character.For example, as shown, in FIG. 2, the computing environment 12 mayinclude a gestures library 190. The gestures library 190 may include acollection of gesture filters, each comprising information concerning agesture that may be performed by the skeletal model (as the user moves).The data captured by the cameras 26, 28 and the capture device 20 in theform of the skeletal model and movements associated with it may becompared to the gesture filters in the gesture library 190 to identifywhen a user (as represented by the skeletal model) has performed one ormore gestures. Those gestures may be associated with various controls ofan application. Thus, the computing environment 12 may use the gestureslibrary 190 to interpret movements of the skeletal model and to controlan application based on the movements.

According to an example embodiment, the capture device 20 may furtherinclude a tilt detection mechanism 50 and a tilt correction mechanism52. The tilt detection mechanism 50 may be a device that may detect atilt or angle of the capture device 20. For example, the tilt detectionmechanism 50 may include a microminiaturized cantilever-type spring thatmay convert a force associated with the tilting of the capture device 20into a measurable displacement associated with a tilt angle of thecapture device 20. Alternatively, the tilt detection mechanism 50 mayinclude a heated gas bubble with one or more thermal sensors. When thecapture device 20 may be tilted the sensors may detect a location of thegas bubble that may be used to determine a tilt angle associated withthe capture device 20. According to example embodiments, the tiltdetection mechanism 50 may be an accelerometer, a potentiometer, a tiltsensor, or any other suitable device that may be used to detect a tiltangle of the capture device 20.

In an example embodiment, the tilt correction mechanism 52 may be adevice that may adjust an angle of the capture device 20. For example,the tilt correction mechanism 52 may be a motor, or the like that may beused to adjust the angle of the capture device 20.

FIG. 3 illustrates an example embodiment of a computing environment thatmay be used to interpret one or more gestures in a target recognition,analysis, and tracking system and/or animate an avatar or on-screencharacter displayed by the target recognition, analysis, and trackingsystem. The computing environment such as the computing environment 12described above with respect to FIGS. 1A-2 may be a multimedia console100, such as a gaming console. As shown in FIG. 3, the multimediaconsole 100 has a central processing unit (CPU) 101 having a level 1cache 102, a level 2 cache 104, and a flash ROM (Read Only Memory) 106.The level 1 cache 102 and a level 2 cache 104 temporarily store data andhence reduce the number of memory access cycles, thereby improvingprocessing speed and throughput. The CPU 101 may be provided having morethan one core, and thus, additional level 1 and level 2 caches 102 and104. The flash ROM 106 may store executable code that is loaded duringan initial phase of a boot process when the multimedia console 100 ispowered ON.

A graphics processing unit (GPU) 108 and a video encoder/video codec(coder/decoder) 114 form a video processing pipeline for high speed andhigh resolution graphics processing. Data is carried from the graphicsprocessing unit 108 to the video encoder/video codec 114 via a bus. Thevideo processing pipeline outputs data to an A/V (audio/video) port 140for transmission to a television or other display. A memory controller110 is connected to the GPU 108 to facilitate processor access tovarious types of memory 112, such as, but not limited to, a RAM (RandomAccess Memory).

The multimedia console 100 includes an I/O controller 120, a systemmanagement controller 122, an audio processing unit 123, a networkinterface controller 124, a first USB host controller 126, a second USBcontroller 128 and a front panel I/O subassembly 130 that are preferablyimplemented on a module 118. The USB controllers 126 and 128 serve ashosts for peripheral controllers 142(1)-142(2), a wireless adapter 148,and an external memory device 146 (e.g., flash memory, external CD/DVDROM drive, removable media, etc.). The network interface 124 and/orwireless adapter 148 provide access to a network (e.g., the Internet,home network, etc.) and may be any of a wide variety of various wired orwireless adapter components including an Ethernet card, a modem, aBluetooth module, a cable modem, and the like.

System memory 143 is provided to store application data that is loadedduring the boot process. A media drive 144 is provided and may comprisea DVD/CD drive, hard drive, or other removable media drive, etc. Themedia drive 144 may be internal or external to the multimedia console100. Application data may be accessed via the media drive 144 forexecution, playback, etc. by the multimedia console 100. The media drive144 is connected to the I/O controller 120 via a bus, such as a SerialATA bus or other high speed connection (e.g., IEEE 1394).

The system management controller 122 provides a variety of servicefunctions related to assuring availability of the multimedia console100. The audio processing unit 123 and an audio codec 132 form acorresponding audio processing pipeline with high fidelity and stereoprocessing. Audio data is carried between the audio processing unit 123and the audio codec 132 via a communication link. The audio processingpipeline outputs data to the A/V port 140 for reproduction by anexternal audio player or device having audio capabilities.

The front panel I/O subassembly 130 supports the functionality of thepower button 150 and the eject button 152, as well as any LEDs (lightemitting diodes) or other indicators exposed on the outer surface of themultimedia console 100. A system power supply module 136 provides powerto the components of the multimedia console 100. A fan 138 cools thecircuitry within the multimedia console 100.

The CPU 101, GPU 108, memory controller 110, and various othercomponents within the multimedia console 100 are interconnected via oneor more buses, including serial and parallel buses, a memory bus, aperipheral bus, and a processor or local bus using any of a variety ofbus architectures. By way of example, such architectures can include aPeripheral Component Interconnects (PCI) bus, PCI-Express bus, etc.

When the multimedia console 100 is powered ON, application data may beloaded from the system memory 143 into memory 112 and/or caches 102, 104and executed on the CPU 101. The application may present a graphicaluser interface that provides a consistent user experience whennavigating to different media types available on the multimedia console100. In operation, applications and/or other media contained within themedia drive 144 may be launched or played from the media drive 144 toprovide additional functionalities to the multimedia console 100.

The multimedia console 100 may be operated as a standalone system bysimply connecting the system to a television or other display. In thisstandalone mode, the multimedia console 100 allows one or more users tointeract with the system, watch movies, or listen to music. However,with the integration of broadband connectivity made available throughthe network interface 124 or the wireless adapter 148, the multimediaconsole 100 may further be operated as a participant in a larger networkcommunity.

When the multimedia console 100 is powered ON, a set amount of hardwareresources are reserved for system use by the multimedia consoleoperating system. These resources may include a reservation of memory(e.g., 16 MB), CPU and GPU cycles (e.g., 5%), networking bandwidth(e.g., 8 kbs), etc. Because these resources are reserved at system boottime, the reserved resources do not exist from the application's view.

In particular, the memory reservation preferably is large enough tocontain the launch kernel, concurrent system applications and drivers.The CPU reservation is preferably constant such that if the reserved CPUusage is not used by the system applications, an idle thread willconsume any unused cycles.

With regard to the GPU reservation, lightweight messages generated bythe system applications (e.g., popups) are displayed by using a GPUinterrupt to schedule code to render popup into an overlay. The amountof memory required for an overlay depends on the overlay area size andthe overlay preferably scales with screen resolution. Where a full userinterface is used by the concurrent system application, it is preferableto use a resolution independent of application resolution. A scaler maybe used to set this resolution such that the need to change frequencyand cause a TV resynch is eliminated.

After the multimedia console 100 boots and system resources arereserved, concurrent system applications execute to provide systemfunctionalities. The system functionalities are encapsulated in a set ofsystem applications that execute within the reserved system resourcesdescribed above. The operating system kernel identifies threads that aresystem application threads versus gaming application threads. The systemapplications are preferably scheduled to run on the CPU 101 atpredetermined times and intervals in order to provide a consistentsystem resource view to the application. The scheduling is to minimizecache disruption for the gaming application running on the console.

When a concurrent system application requires audio, audio processing isscheduled asynchronously to the gaming application due to timesensitivity. A multimedia console application manager (described below)controls the gaming application audio level (e.g., mute, attenuate) whensystem applications are active.

Input devices (e.g., controllers 142(1) and 142(2)) are shared by gamingapplications and system applications. The input devices are not reservedresources, but are to be switched between system applications and thegaming application such that each will have a focus of the device. Theapplication manager preferably controls the switching of input stream,without knowledge the gaming application's knowledge and a drivermaintains state information regarding focus switches. The cameras 26, 28and capture device 20 may define additional input devices for theconsole 100.

FIG. 4 illustrates another example embodiment of a computing environment220 that may be the computing environment 12 shown in FIGS. 1A-2 used tointerpret one or more gestures in a target recognition, analysis, andtracking system and/or animate an avatar or on-screen characterdisplayed by a target recognition, analysis, and tracking system. Thecomputing system environment 220 is only one example of a suitablecomputing environment and is not intended to suggest any limitation asto the scope of use or functionality of the presently disclosed subjectmatter. Neither should the computing environment 220 be interpreted ashaving any dependency or requirement relating to any one or combinationof components illustrated in the exemplary operating environment 220. Insome embodiments the various depicted computing elements may includecircuitry configured to instantiate specific aspects of the presentdisclosure. For example, the term circuitry used in the disclosure caninclude specialized hardware components configured to performfunction(s) by firmware or switches. In other examples embodiments theterm circuitry can include a general purpose processing unit, memory,etc., configured by software instructions that embody logic operable toperform function(s). In example embodiments where circuitry includes acombination of hardware and software, an implementer may write sourcecode embodying logic and the source code can be compiled into machinereadable code that can be processed by the general purpose processingunit. Since one skilled in the art can appreciate that the state of theart has evolved to a point where there is little difference betweenhardware, software, or a combination of hardware/software, the selectionof hardware versus software to effectuate specific functions is a designchoice left to an implementer. More specifically, one of skill in theart can appreciate that a software process can be transformed into anequivalent hardware structure, and a hardware structure can itself betransformed into an equivalent software process. Thus, the selection ofa hardware implementation versus a software implementation is one ofdesign choice and left to the implementer.

In FIG. 4, the computing environment 220 comprises a computer 241, whichtypically includes a variety of computer readable media. Computerreadable media can be any available media that can be accessed bycomputer 241 and includes both volatile and nonvolatile media, removableand non-removable media. The system memory 222 includes computer storagemedia in the form of volatile and/or nonvolatile memory such as readonly memory (ROM) 223 and random access memory (RAM) 260. A basicinput/output system 224 (BIOS), containing the basic routines that helpto transfer information between elements within computer 241, such asduring start-up, is typically stored in ROM 223. RAM 260 typicallycontains data and/or program modules that are immediately accessible toand/or presently being operated on by processing unit 259. By way ofexample, and not limitation, FIG. 4 illustrates operating system 225,application programs 226, other program modules 227, and program data228.

The computer 241 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 4 illustrates a hard disk drive 238 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 239that reads from or writes to a removable, nonvolatile magnetic disk 254,and an optical disk drive 240 that reads from or writes to a removable,nonvolatile optical disk 253 such as a CD ROM or other optical media.Other removable/non-removable, volatile/nonvolatile computer storagemedia that can be used in the exemplary operating environment include,but are not limited to, magnetic tape cassettes, flash memory cards,digital versatile disks, digital video tape, solid state RAM, solidstate ROM, and the like. The hard disk drive 238 is typically connectedto the system bus 221 through an non-removable memory interface such asinterface 234, and magnetic disk drive 239 and optical disk drive 240are typically connected to the system bus 221 by a removable memoryinterface, such as interface 235.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 4, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 241. In FIG. 4, for example, hard disk drive 238 is illustratedas storing operating system 258, application programs 257, other programmodules 256, and program data 255. Note that these components can eitherbe the same as or different from operating system 225, applicationprograms 226, other program modules 227, and program data 228. Operatingsystem 258, application programs 257, other program modules 256, andprogram data 255 are given different numbers here to illustrate that, ata minimum, they are different copies. A user may enter commands andinformation into the computer 241 through input devices such as akeyboard 251 and pointing device 252, commonly referred to as a mouse,trackball or touch pad. Other input devices (not shown) may include amicrophone, joystick, game pad, satellite dish, scanner, or the like.These and other input devices are often connected to the processing unit259 through a user input interface 236 that is coupled to the systembus, but may be connected by other interface and bus structures, such asa parallel port, game port or a universal serial bus (USB). The cameras26, 28 and capture device 20 may define additional input devices for theconsole 100. A monitor 242 or other type of display device is alsoconnected to the system bus 221 via an interface, such as a videointerface 232. In addition to the monitor, computers may also includeother peripheral output devices such as speakers 244 and printer 243,which may be connected through a output peripheral interface 233.

The computer 241 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer246. The remote computer 246 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 241, although only a memory storage device 247 has beenillustrated in FIG. 4. The logical connections depicted in FIG. 2include a local area network (LAN) 245 and a wide area network (WAN)249, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 241 is connectedto the LAN 245 through a network interface or adapter 237. When used ina WAN networking environment, the computer 241 typically includes amodem 250 or other means for establishing communications over the WAN249, such as the Internet. The modem 250, which may be internal orexternal, may be connected to the system bus 221 via the user inputinterface 236, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 241, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 4 illustrates remoteapplication programs 248 as residing on memory device 247. It will beappreciated that the network connections shown are exemplary and othermeans of establishing a communications link between the computers may beused.

FIG. 5 depicts a flow diagram of an example method 300 for detecting atilt angle of a capture device. The example method 300 may beimplemented using, for example, the capture device 20 and/or thecomputing environment 12 of the target recognition, analysis, andtracking system 10 described with respect to FIGS. 1A-4. In an exampleembodiment, the example method 300 may take the form of program code(i.e., instructions) that may be executed by, for example, the capturedevice 20 and/or the computing environment 12 of the target recognition,analysis, and tracking system 10 described with respect to FIGS. 1A-4.

According to one embodiment, at 305, a depth image may be received. Forexample, the target recognition, analysis, and tracking system mayinclude a capture device such as the capture device 20 described abovewith respect to FIGS. 1A-2. The capture device may capture or observe ascene that may include one or more targets. In an example embodiment,the capture device may be a depth camera configured to obtain an imagesuch as an a depth image of the scene using any suitable technique suchas time-of-flight analysis, structured light analysis, stereo visionanalysis, or the like.

The depth image may be a plurality of observed pixels where eachobserved pixel has an observed depth value. For example, the depth imagemay include a two-dimensional (2-D) pixel area of the captured scenewhere each pixel in the 2-D pixel area may have a depth value such as alength or distance in, for example, centimeters, millimeters, or thelike of an object in the captured scene from the capture device.

FIG. 6 illustrates an example embodiment of a depth image 400 that maybe received at 305. According to an example embodiment, the depth image400 may be an image or frame of a scene captured by, for example, the3-D camera 26 and/or the RGB camera 28 of the capture device 20described above with respect to FIG. 2. As shown in FIG. 6, the depthimage 400 may include a human target 402 corresponding to, for example,a user such as the user 18 described above with respect to FIGS. 1A and1B and one or more non-human targets 404 such as a wall, a table, amonitor, or the like in the captured scene. As described above, thedepth image 400 may include a plurality of observed pixels where eachobserved pixel has an observed depth value associated therewith. Forexample, the depth image 400 may include a two-dimensional (2-D) pixelarea of the captured scene where each pixel in the 2-D pixel area mayrepresent a depth value such as a length or distance in, for example,centimeters, millimeters, or the like of a target or object in thecaptured scene from the capture device. In one embodiment, the depthimage 400 may be colorized such that different colors of the pixels ofthe depth image correspond to and/or visually depict different distancesof the human target 402 and non-human targets 404 from the capturedevice. For example, according to one embodiment, the pixels associatedwith a target closest to the capture device may be colored with shadesof red and/or orange in the depth image whereas the pixels associatedwith a target further away may be colored with shades of green and/orblue in the depth image.

Referring back to FIG. 5, in one embodiment, upon receiving the image,at 305, the image may be downsampled to a lower processing resolutionsuch that the depth image may be more easily used and/or more quicklyprocessed with less computing overhead. Additionally, one or morehigh-variance and/or noisy depth values may be removed and/or smoothedfrom the depth image; portions of missing and/or removed depthinformation may be filled in and/or reconstructed; and/or any othersuitable processing may be performed on the received depth informationmay such that the depth information may used to generate a model such asa skeletal model, which will be described in more detail below.

At 315, a human target in a depth image may be scanned for one or morebody parts. For example, upon receiving a depth image, the targetrecognition, analysis, and tracking system may determine whether thedepth image includes a human target such as the human target 402described above with respect to FIG. 6 corresponding to, for example, auser such as the user 18, described above with respect to FIGS. 1A-1B.In one embodiment, to determine whether the depth image includes a humantarget, the target recognition, analysis, and tracking system may floodfill each target or object in the depth image and may compare each floodfilled target or object to a pattern associated with a body model of ahuman in various positions or poses. The flood filled target, or thehuman target, that matches the pattern may then be scanned to determinevalues including, for example, locations and/or measurements such aslength, width, or the like associated with one or more body parts. Forexample, the flood filled target, or the human target, that matches thepattern may be isolated and a mask of the human target may be created.The mask may be created by, for example, flood filling the human targetsuch that the human target may be separated from other targets orobjects in the scene elements. The mask may then be analyzed todetermine the locations and/or measurements for one or more body parts.According to one embodiment, a model such as a skeletal model, a meshhuman model, or the like of the human target may be generated based onthe locations and/or measurements for the one or more body parts.

In one embodiment, the target recognition, analysis, and tracking systemmay determine whether a human target in the depth image may have beenpreviously scanned before the human target may be scanned at 315. Forexample, the capture device such as the capture device 20 describedabove with respect to FIGS. 1A-2 may capture a scene in frames. Eachframe may include a depth image. The depth image of each frame may beanalyzed to determine whether the depth image may include a human targetas described above. The depth image of each frame may further beanalyzed to determine whether the human target may have been previouslyscanned for one or more body parts. For example, the target recognition,analysis, and tracking system may determine whether a human target inthe depth image received, at 305, corresponds to a human targetpreviously scanned. In one embodiment, if the human target may notcorrespond to a human target previously scanned, the human target maythen be scanned at 315. Thus, according to an example embodiment, ahuman target may be scanned once in an initial frame and initial depthimage captured by the capture device that includes the human target.

According to another embodiment, the target recognition, analysis, andtracking system may scan the human target for one or more body parts ineach received depth image that includes the human target. The scanresults associated with, for example, the measurements for the one ormore body parts may then be averaged.

Additionally, in an example embodiment, the target recognition,analysis, and tracking system may determine whether to scan a humantarget in the depth image, at 310, before the human target may bescanned at 315. For example, the target recognition, analysis, andtracking system may analyze the depth image to determine whether thedepth image includes a human target, whether a human target may be in aparticular pose such as a standing pose with arms to each side to bescanned, a T-pose or, or any other suitable pose before the targetrecognition, analysis, and tracking system may scan the human target at315. The target recognition, analysis, and tracking system may then scanthe human target at 315 based on the analysis at 310. For example, thetarget recognition analysis, and tracking system may scan the humantarget at 315 if, based on the analysis, at 310 the depth image includesa human target, a human target in the depth image may be in a particularpose, or the like.

FIG. 7 illustrates an example embodiment of a depth image 400 that mayinclude a human target 402 that may be scanned at, for example, 315. Forexample, after a valid human target such as the human target 402 may befound within the depth image 400, the background or the area of thedepth image not matching the human target may be removed. A mask maythen be generated for the human target 402 that may include values ofthe human target along, for example, an X, Y, and Z axis. According toan example embodiment, the mask of the human target 402 may be scannedfor various body parts, starting with, for example, the head to generatea skeletal model of the human target 402.

As shown in FIG. 7, the information such as the bits, pixels, or thelike associated with the matched human target 402 may be scanned todetermine various locations such as scan bp1-scan bp6 that areassociated with various parts of the body of the human target 402. Forexample, after removing the background or area surrounding the humantarget 402 in the depth image, the depth image 400 may include the humantarget 402 isolated. The mask that may include X, Y, and Z values maythen be generated for the isolated human target 402. The mask of thehuman target 402 may be scanned to determine a location, a measurement,and other information of various body parts. For example, a top of themask of the human target 402 may initially be determined. As shown inFIG. 7, the top of the mask of the human target 402 may be associatedwith a location of the top of the head as indicated by scan bp1. Afterdetermining the top of the head, the bitmask may be scanned downward tothen determine a location of a neck of the human target 402, a locationof the shoulders of the human target 402, or the like.

According to an example embodiment, to determine the location of theneck, shoulders, or the like of the human target 402, a width of themask, for example, at a position being scanned, may be compared to athreshold value of a typical width associated with, for example, a neck,shoulders, or the like. In an alternative embodiment, the distance froma previous position scanned and associated with a body part in a maskmay be used to determine the location of the neck, shoulders or thelike.

Additionally, some body parts such as legs, feet, or the like may becalculated based on, for example, the location of other body parts. Forexample, as described above, the information such as the bits, pixels,or the like associated with the human target 402 may be scanned todetermine the locations of various body parts of the human target 402represented by scan bp1-scan bp6 in FIG. 7. Based on such locations,subsequent body parts such as legs, feet, or the like may then becalculated for the human target 402.

According to an example embodiment, upon determining the values of, forexample, a body part, a data structure may be created that may includelocation and/or measurement values such as length, width, or the like ofthe body part associated with the scan of the bitmask of the humantarget 402. In one embodiment, the data structure may include scanresults averaged from a plurality depth images. For example, asdescribed above, the capture device such as the capture device 20described above with respect to FIGS. 1A-2 may capture a scene inframes. Each frame may include a depth image. The depth image of eachframe may be analyzed to determine whether a human target may beincluded as described above. If the depth image of a frame includes ahuman target, a mask of the human target of the depth image associatedwith the frame may be scanned for one or more body parts at 310. Thedetermined value of a body part for each frame may then be averaged suchthat the data structure may include average measurement values such aslength, width, or the like of the body part associated with the scans ofeach frame. According another embodiment, the measurement values of thedetermined body parts may be adjusted such as scaled up, scaled down, orthe like such that measurements values in the data structure moreclosely correspond to a typical model of a human body.

FIG. 8 illustrates an example embodiment of a depth image with a humantarget that may have been scanned. As shown in FIG. 8, a model 500 ofthe human target may be generated based on the scan. For example,according to one embodiment, measurement values determined by thescanned mask may be used to define one or more joints in, for example, askeletal model such as the model 500. The one or more joints may be usedto define one or more bones that may correspond to a body part of ahuman. According to an example embodiment, the model 500 may include oneor more data structures such as mathematical vectors that may definejoints and bones of the skeletal model 500 including the measurementsand locations of the one or more body parts associated with the jointsand bones.

Referring back to FIG. 5, at 320, a tilt angle may be calculated. Forexample, in one embodiment, the capture device such as the capturedevice 20 described above with respect to FIGS. 1A-2 may be tiltedupward or downward. Information including the depth images captured bythe capture device may be distorted or skewed based on the tilt. Forexample, the depth values associated with the targets or objects in acaptured depth image may be inaccurate (i.e. not upright) due to anangle associated with the tilt of the capture device.

According to an example embodiment, the model such as the model 500described above with respect to FIG. 8 that may be generated from theinformation may also be skewed based on the tilt. In one embodiment, ifthe depth values associated with the targets or objects in a captureddepth image may be inaccurate, the model generated based on those valuesmay also be inaccurate. For example, if the capture device may be tilteddown on a scene, body parts such as the head, shoulders, or the like atthe top portion of a human may be closer to the capture device and havenearer depth values than body parts such as the hips, legs, or the likeat the lower portion of a human. Depending on the severity of thedownward tilt of the capture device, the discrepancy in the depth valuesmay cause the measurements of the one or more body parts determinedbased on the scan to be inaccurate such that the model based on thosemeasurements may also be inaccurate.

At 320, the target recognition, analysis, and tracking system maycalculate an angle associated with an upward or downward tilt of thecapture device such that the distorted or skewed information may beadjusted based on the calculated tilt angle, which will be described inmore detail below. For example, after scanning the human target at 315,the target recognition, analysis, and tracking system may identify orselect, for example, a first portion of the human target associated withan upper body part such as the shoulders of the human target and asecond portion of the human target associated with a lower body partsuch as a midpoint between the hips and knees. The target recognition,analysis, and tracking system may then calculate the tilt angle based onthe first and second portions of the human target. For example, thefirst and second portions may define a line therebetween. According toan example embodiment, the line may be used to calculate a tangent valuethat may be used to determine the tilt angle, which will be described inmore detail below.

FIG. 9 illustrates an example embodiment of pixels 420 that may definethe human target 402 in, for example, the depth image 400 describedabove with respect to FIG. 6. For example, the pixels 420 may be aportion or part of the pixels in the 2-D pixel area of the first depthimage 400 that may define the human target 402. According to oneembodiment, each of the pixels 420 may include a depth value associatedtherewith that may represent the length or distance in, for example,centimeters, millimeters, or the like of a body part of the human target402 from the capture device.

As shown in FIG. 9, the human target 402 may include a first portion 422of pixels and a second portion 424 of pixels. According to an exampleembodiment, the first and second portions 422, 424 of pixels may beassociated with a location of an upper body part of the human target anda lower body part of the target respectively. For example, as describedabove, the target recognition, analysis, and tracking system may scan ahuman target such as the human target 402 described above with respectto FIGS. 6-8 to determine the location and measurements of one or morebody parts. Upon determining the location and measurements of the one ormore body parts, the target recognition, analysis, and tracking systemmay identify or select a first portion such as the first portion 422associated with, for example, an upper body part such as the shouldersof the human target 402 determined by scan. Thus, in one embodiment,upon determining the location and/or measurements of the shoulders, thetarget recognition, analysis, and tracking system may compare thelocation and/or measurements of, for example, the shoulders, with a maskof the human target 402 in the depth image 400. The target recognition,analysis, and tracking system may then identify a portion of pixels suchas the portion 422 that may correspond to the location and/ormeasurements of the shoulders.

The target recognition, analysis, and tracking system may furtheridentify or select a second portion such as the second portion 424associated with, for example, lower body part or torso such as amidpoint between the hips and the knees of the human target 402determined by scan. Thus, in one embodiment, upon determining thelocation and/or measurements of the hips and knees, the targetrecognition, analysis, and tracking system may compare the locationand/or measurements of, for example, the hips and knees, with the maskof the human target 402 in the depth image 400. The target recognition,analysis, and tracking system may then identify a portion of pixels suchas the portion 424 that may correspond to the location and/ormeasurements of a midpoint between the hips and knees. According to anexample embodiment, the first and second portions 422, 424 of the pixelsmay define a line therebetween that may be used to calculate a tiltangle, which will be described in more detail below.

FIGS. 10A-10B illustrate an example embodiment of the first and secondportions 422, 424 of pixels associated with a human target in a depthimage that may be used to calculate a tilt angle for a capture device.As described above, the first portion 422 may include a strip, arectangle, or any suitable region of pixels along a first body part suchas the shoulders of the human target 402 that may be determined by thescan and the second portion 424 may include a strip, a rectangle or anysuitable region of pixels along a second body part such as a midpointbetween the hips and knees of the human target that may be determined bythe scan.

As shown in FIG. 10A, each of the pixels in the first portion 422 mayhave a depth value. According to one embodiment, a first average depthvalue based on the depth values for each of the pixels in the firstportion 422 may be calculated. For example, the depth values for each ofthe pixels in the first portion 422 may be added together to calculate afirst sum depth value for the first portion 422. The first sum depthvalue may then be divided by a total number of valid depth pixels in thefirst portion 422 to calculate the first average depth value for thefirst portion 422.

For example, as shown in FIG. 10A, the depth values for each of thepixels in the first portion 422 may be added together to calculate afirst sum depth value of 513. The first sum depth value of 513 may bedivided by the total number of pixels, 23, of the first portion 422 tocalculate a first average depth value of 22.3 for the first portion 422.

Similarly, as shown in FIG. 10B, each of the pixels in the secondportion 424 may have a depth value. According to one embodiment, asecond average depth value based on the depth values for each of thepixels in the second portion 424 may also be calculated. For example,the valid depth values for each of the pixels in the second portion 422may be added together to calculate a second sum depth value for thesecond portion 424. The second sum depth value may then be divided by atotal number of pixels in the second portion 424 to calculate the secondaverage depth value for the second portion 424.

For example, as shown in FIG. 10B, the depth values for each of thepixels in the second portion 424 may be added together to calculate asecond sum depth value of 678. The second sum depth value of 678 may bedivided by the total number of pixels, 19, of the second portion 424 tocalculate an average depth value of 35.7 for the second portion 424.

FIG. 11 illustrates a side view of an example embodiment of a depthimage 400 with a human target 402 that may be tilted. As shown in FIG.11, in an example embodiment, a line X may be defined between the firstand second portions 422, 424 of pixels described above in FIGS. 9-10Bthat may be used to calculate a tilt angle. For example, the line X maybe used to define a hypotenuse of a right triangle as shown in FIG. 11.In one embodiment, an angle T that may be the angle associated with thetilt angle may be calculated based on the arctangent of the second valueΔz associated with a line opposite of the angle T divided by the firstvalue Δy associated with a line adjacent to the angle T. According toanother example embodiment, an angle A may be calculated based on thearctangent of a first value Δy associated with a line opposite of theangle A divided by a second value Δz associated with a line adjacent tothe angle A. The angle A may then be subtracted from 90 degrees todetermine the angle T that may angle associated with the tilt angle.

According to an example embodiment, the first value Δy may be thevertical distance between the first portion 422 and the second portion424 of pixels described above. For example, each of the pixelsassociated with the first portion 422 may have a first Y valuerepresenting the distance of, for example, the first portion from thebottom of the depth image. Additionally, each of the pixels associatedwith the second portion 422 may have a second Y value representing thedistance of, for example, the second portion 424 from the bottom of thedepth image. The first value Δy may be the difference between the firstand second Y values of the first and second portions 422, 424. Forexample, in one embodiment, the first Y value associated with the firstportion 422 may be 220 and the second Y value associated with the secondportion 424 may be 130 such that the first value Δy may be 90 or thedifference between the first Y value and the second Y value.

In one embodiment, the second value Δz may be the difference between theaverage depth values calculated for the first and second portions 422,424, as described above. For example, as described above with respect toFIGS. 10A-10B, the first average depth value associated with the firstportion 422 may be 22.3 and the second average depth value associatedwith the second portion 424 of pixels may be 35.7. According to anexample embodiment, the second value Δz may be 13.4, which is thedifference between the first average depth value of 22.3 and the secondaverage depth value of 35.7 for the respective first and second portions422, 424.

According to one embodiment, the angle T that may be the angle of thetilt angle may be calculated based on the arctangent of the second valueΔz divided by the first value Δy. Thus, if the first value Δy may be 90and the second value Δz may be 13.4 as described above, the angle A maybe the tan⁻¹ (13.4/90) or 8.5 degrees.

As described above, in another example embodiment, the angle A may becalculated based on the arctangent of the first value Δy divided by thesecond value Δz. Thus, if the first value Δy may be 90 and the secondvalue Δz may be 13.4 as described above, the angle A may be the tan⁻¹(90/13.4) or 81.5 degrees. In an example embodiment, the tilt angle maythen be determined based on the angle A. For example, the tilt angle maybe calculated by subtracting the angle A from the angle of the humantarget when the camera may not be tilted, or 90 degrees. Thus, asdescribed above, if the angle A is 81.5 degrees, the tilt angle may be90 degrees minus 81.5 degrees, or 8.5 degrees.

Referring back to FIG. 5, the target recognition, analysis, and trackingsystem may determine, at 325, whether to receive a subsequent frame. Forexample, as described above, the capture device such as the capturedevice 20 described above with respect to FIGS. 1A-2 may capture a scenein frames. Each frame may include a depth image. In an exampleembodiment, the tilt angle may be calculated for and averaged with depthimages in a series of the frames. For example, the target recognition,analysis, and tracking system may receive a first depth image of thefirst frame, at 305, that may be used to calculate a first tilt angle at320 as described above. If the target recognition, analysis and trackingsystem determines to receive a second frame to calculate the tilt angle,at 325, the target recognition, analysis and tracking system may receivea second depth image associated with the second frame at 305. A secondtilt angle may then be calculated at 320 as described above. The firstand second tilt angles may then be averaged together, at 320, tocalculate the tilt angle. Thus, in one embodiment, the targetrecognition, analysis, and tracking system may average the first tiltangle with tilt angles over, for example, the tilt angles calculated foreach of the n frames to generate the tilt angle.

At 325, if the target recognition, analysis, and tracking systemdetermines not to receive a subsequent frame, the tilt angle may beprocessed at 33. According to one embodiment, the tilt angle may beprocessed to physically adjust a capture device, the target human modelbased on the tilt angle and/or transform (i.e. rotate) the captureddepth image and/or RGB image from the capture device at 330. Forexample, a capture device such as the capture device 20 described abovewith respect to FIGS. 1A-2 may include a tilt correction mechanism suchthe tilt correction mechanism 52. According to an example embodiment,the tilt correction mechanism may adjust the capture device in anappropriate direction such as upward or downward by, for example, thetilt angle.

Additionally, as described above, the target recognition, analysis, andtracking system may generate a model such as a skeletal model, a meshmodel, or the like based on the scan at 315. According to an exampleembodiment, the model may be adjusted in an appropriate direction suchas forward or backward by, for example, the tilt angle.

According to another embodiment, the target recognition, analysis, andtracking system may process the tilt angle to determine a background ora non-player environment of the depth image, determine skewed depthvalues, or may adjust any other information such as RGB images, IR data,or the like that may be included in the target, analysis, and trackingsystem.

It should be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered limiting. The specificroutines or methods described herein may represent one or more of anynumber of processing strategies. As such, various acts illustrated maybe performed in the sequence illustrated, in other sequences, inparallel, or the like. Likewise, the order of the above-describedprocesses may be changed.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

What is claimed:
 1. A system, comprising: a camera; a processor; andmemory communicatively coupled to the processor, the memory bearingcomputer-readable instructions that, in response to execution by theprocessor, cause the system to perform operations comprising:determining, using relative position of pixels in an image captured bythe camera, a tilt angle indicating an angle the camera is tilted upwardor downward; and modifying, based at least in part on the determinedtilt angle, data captured by the camera.
 2. The system of claim 1,wherein the computer-readable instructions cause the system to performoperations further comprising: modifying a position of the camera basedat least in part on the tilt angle.
 3. The system of claim 2, whereinmodifying a position of the camera based at least in part on the tiltangle comprises: rotating the camera in an upward direction in responseto determining that the camera is angled downward.
 4. The system ofclaim 2, wherein modifying a position of the camera based at least inpart on the tilt angle comprises: rotating the camera in a downwarddirection in response to determining that the camera is angled upward.5. The system of claim 1, wherein modifying, based at least in part onthe determined tilt angle, data captured by the camera comprises:modifying depth data received by the camera based at least in part onthe tilt angle.
 6. The system of claim 1, wherein modifying, based atleast in part on the determined tilt angle, data captured by the cameracomprises: determining a depth value of a plurality of depth values inthe data of a capture area to be modified based on the tilt angle. 7.The system of claim 1, wherein modifying, based at least in part on thedetermined tilt angle, data captured by the camera comprises: modifyinga color or infrared image of a capture area received by the camera basedon the tilt angle.
 8. The system of claim 1, wherein modifying, based atleast in part on the determined tilt angle, data captured by the cameracomprises: rotating a color or depth image of a capture area received bythe camera based on the tilt angle.
 9. The system of claim 1, whereinthe computer-readable instructions cause the system to performoperations further comprising: adjusting a computer model thatrepresents a person depicted in an image of a capture area received bythe camera component based on the tilt angle.
 10. The system of claim 9,wherein adjusting a computer model that represents a person depicted inan image of a capture area received by the camera component based on thetilt angle comprises: rotating the computer model forward or backward bya number of degrees equal to a number of degrees in the tilt angle. 11.The system of claim 1, wherein the computer-readable instructions causethe system to perform operations further comprising: determining abackground depicted in an image of the capture area received by thecamera component based on the tilt angle.
 12. A method, comprising:determining, by one or more computers, using relative position of pixelsin an image captured by a camera, a tilt angle that indicates an anglethat the camera is tilted upward or downward; and modifying, by the oneor more computers, based at least in part on the determined tilt angle,data captured by the camera.
 13. The method of claim 12, furthercomprising: modifying a position of the camera based at least in part onthe determined tilt angle.
 14. The method of claim 13, wherein modifyingthe position of the camera based at least in part on the determined tiltangle further comprises: rotating the camera in an upward direction inresponse to determining that the camera is angled downward, and rotatingthe camera in a downward direction in response to determining that thecamera component is angled upward.
 15. The method of claim 12, furthercomprising: adjusting a computer model that represents a person depictedin an image of the capture area received by the camera based on the tiltangle.
 16. The method of claim 15, wherein adjusting the computer modelthat represents the person further comprises: rotating the computermodel forward or backward by a number of degrees equal to a number ofdegrees in the tilt angle.
 17. The method of claim 12, furthercomprising: determining a background depicted in an image of the capturearea received by the camera component based on the tilt angle.
 18. Acomputer-readable storage device, bearing computer-executableinstructions that, in response to execution on a computer, cause thecomputer to perform operations comprising: determining, using relativeposition of pixels in an image captured by a camera, a tilt angle thatindicates an angle that the camera is tilted upward or downward; andmodifying, based at least in part on the determined tilt angle, datacaptured by the camera.
 19. The computer-readable storage device ofclaim 18, wherein modifying data captured by the camera comprisesmodifying the image captured by the camera.
 20. The computer-readablestorage device of claim 19, wherein modifying data captured by thecamera comprises determining a depth value of a plurality of depthvalues in the data captured by the camera.